1. Field of the Invention
The present invention relates to a method for manufacturing extended-wing capacitors, especially to the formation of high-density capacitors in tiny memory cells having high cell capacitance.
2. Description of Related Art
To manufacture advanced memory devices, the packing density of memory cells has to be increased multifold. This new design trend has had a tremendous impact on memory cell capacitors. Since the space for capacitors has to be smaller to fit in the new memory design, the capacitance of capacitors in memory cells is adversely affected. Therefore, a challenge in the process of manufacturing memory cells is how to maintain appropriate cell capacitance within the space constraint. The most difficult task is how to control the spacing between the plate electrodes, and the spacing between the insulating film and these two plate electrodes.
Among the efforts to maintain appropriate cell capacitance in high-density memory devices, the notion of a stacked capacitor (STC) structure is suggested. Since cylindrical or concave stacked capacitors are oval shaped, controlling the thickness of the high-k insulation film and the deposition of the top plate becomes very difficult when using these types of capacitors in tiny memory cells. The problem is especially severe when using materials such as BST, SrTiO3 and PZT to form the high-k insulation film in cylindrical and concave stacked capacitors.
On the other hand, for convex stacked capacitors, the problem with spacing and deposition can be corrected considerably, but the surface area of the plate electrodes in convex stacked capacitors is even smaller. The resultant cell capacitance is only 0.6xc3x97 that of cylindrical type capacitors.
To overcome the shortcomings in the prior art previously mentioned, a novel method for the manufacture of cell capacitors with wing extensions is devised.
The main objective of the present invention is to provide a method for manufacturing extended-wing capacitors in memory cells. The arrangement of contact areas is such that two adjacent contact areas are in alternating positions, rather than being juxtaposed as in the prior art. The wing-like plate electrode is formed over a contact area, vertically over the contact area and extending laterally towards a neighboring contact area. This type of plate electrode with a wing extension is capable of improving the cell capacitance, because the effective surface area of the plate is increased by a significant amount.
Another objective of the present invention is to use generally applied conventional techniques such as photo etching, etching, and deposition to carry out the method for manufacturing extended-wing capacitors in memory cells. Use of generally applied, conventional techniques will ensure that the manufacturing process can be well controlled and the manufacturing yield can be maintained at high levels.
The method for the manufacture of extended-wing capacitors in memory cells comprises the steps of:
(1) forming multiple contact areas to be disposed in alternate positions;
(2) depositing electroplating base material (EBM) over the substrate including the alternate contact areas, patterned to form transversal parallel slabs;
(3) covering the EBM layer with insulating film, patterned to form longitudinal parallel lines, such that the insulating lines and EBM slabs together form a crisscross pattern, separating the EBM slabs into multiple segments;
(4) electroplating conductive material on the exposed area of EBM to form an electrode layer; and
(5) removing the insulating film and EBM, thus a plate electrode is formed over a contact area.
The design of this capacitor is such that the plate electrode is formed vertically over each contact area and two adjacent contact areas are disposed in alternate positions to accommodate the lateral wing extension of the plate electrode. Under such design, the surface area of a plate electrode can be increased by large proportions. Therefore, using this method high-density memory device can be manufactured with high cell capacitance. Since the plate electrode is formed by conventional electroplating, the manufacturing process can be well controlled, allowing the manufacturing yield to be maintained at high levels even for tiny memory cells with very small space.